Method for data preparation and watermark insertion

ABSTRACT

A method for data preparation and watermark insertion. The method includes the step of preparing the data at a first time by manipulating at least one set of the data characteristics for subsequent insertion of a first watermark. In a preferred embodiment of the method of the present invention the method further includes the step of inserting the first watermark by manipulating the set of data characteristics at a second time subsequent to the first time. In still yet another preferred embodiment of the method of the present invention, the method further includes the step of inserting a second watermark at a third time, before, during, or after the first time, by manipulating at least one set of the data characteristics. In a variation of the present invention a method for inserting a watermark into compressed data is provided. The compressed data has sets of data characteristics. The method includes the steps of inserting a watermark by manipulating the set of data characteristics; and optimizing the manipulated data by modifying the compressed data characteristics subject to a set of constraints.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to preventing unlawful copyingof audio, video and other media that can be digitized and, moreparticularly, to a method for inserting a watermark into digitized data.

2. Prior Art

Methods are known to insert a watermark into an image or audio or videodata. One purpose of such a watermark is for copy generation management,e.g. Allowing a single generation of copies to be made from a master,but no subsequent copies to be made from the first generation copies.

In such an application, there are three states that must be represented“copy never”, “copy once” and “copy no more”. The “copy never” state isintended to prohibit any copying of the content. The “copy once” stateis intended to permit a single generation of copying. As such, this onegeneration copy must have its state changed from the original “copyonce” to the “copy no more” state.

The copy generation management can be implemented in a variety of ways.One solution is to use two different watermarks to encode the states“copy never” and “copy once” in the original material. Then, when a copyis made, an additional watermark is inserted that indicates the state“copy no more”. Several variations of this method are possible. First,the “copy once” watermark may be removed prior to the insertion of the“copy no more” watermark. In practice, this is probably unnecessarysince more than one watermark can co-exist in the data. Also, if thewatermark is easily removable, then it may be straightforward tocircumvent the copy generation management system by simply removing the“copy once” watermark from the content. Content with no watermark isassumed to be freely Copiague.

Second, the “copy once” state may be represented by the existence of twowatermarks. One watermark would be difficult to remove and, whendetected in isolation, would represent the “copy no more” state. Thesecond watermark would be easy to remove and would only have meaningwhen detected in conjunction with the “copy no more” watermark,detection of both watermarks would represent the “copy once” state. Anadvantage of this approach is that, if carefully designed, the fragilewatermark would be automatically removed by the existing installed baseof VHS tape recorders. Note, however, that the fragile watermark muststill survive signal processing that is common to video post productionand transmission, e.g. low pass filtering, color correction and MPEG-2compression.

Watermarks are typically inserted as noise in the digital signal duringthe production stage. The insertion of the watermark can be accomplishedby many different procedures known in the art. The watermark, althoughinserted as noise, must be invisible to human perception or the imagequality will suffer. Thus watermarks inserted at the production stageare image dependent and require great computational effort to ensurethat the watermark will be invisible but robust enough so that it willsurvive post signal processing.

Once inserted, it is necessary to detect the presence of the watermarkat a subsequent time. A typical method for determining the presence of awatermark in suspect data is to compare some characteristic of the dataor signal derived from the data characteristics to a target watermarkpattern. The watermark is determined to be present if this comparisonindicates sufficient similarity.

A typical method of the prior art for watermarking data is illustratedin FIG. 1. FIG. 1 shows three similar data sets and, above each, thesignal that would be derived from the data characteristics duringdetection. To the original data 1 a watermark pattern 2 is added. Thesum of these two signals is the watermarked data 3. During the detectionprocess a signal derived from data characteristics 6 is extracted fromthe watermarked data 3 and compared to a target watermark pattern 5. Thewatermarked data 3 is the sum of the original data 1 and the watermarkpattern 2. This may be a predetermined linear or non-linear combination.The signal derived from the data characteristics 6, in this example is alinear (or perhaps non-linear) combination of a signal derived from theoriginal data 4 and the target watermark pattern 5. In general, thecharacteristics of the watermark and those of the original data willinteract and thus the signal derived from the characteristics of thewatermarked data 6 and that derived from the characteristics of thewatermark 5 will not exactly match. The similarity of the signal derivedfrom the characteristics of the watermarked data 6 and the signalderived from the characteristics of the watermark 5 indicates thelikelihood that the data contains the watermark 2. Note that in thisillustration, the signal derived from the characteristics of thewatermarked data 6 is similar to the signal derived from thecharacteristics of the watermark 5 suggesting the watermark 2 is presentin the watermarked data 3, but the signal derived from the original data4 and the signal derived from the characteristics of the watermarkeddata 6 are dissimilar, indicating that the original data 1 does not yetcontain the watermark 2.

Note that in FIG. 1, it is desirable for the watermarking process togenerate watermarked data 3 such that the extracted signal 6 ismaximally similar to the target watermark 5. In many cases thissimilarity is increased as the relative amplitude or strength of thewatermark pattern 2, and thus the signal extracted from the datacharacteristics 5, is increased. The drawback to increasing thewatermark strength is that this also tends to decrease the similaritybetween the watermarked and original data 3, 1, respectively. Generally,in the case where the data represents audio, video, or imagery, thissimilarity is judged by the human visual and auditory systems. Thus,increasing the watermark strength often leads to a loss of audio, video,or image quality.

A typical approach of the prior art to addressing these apparentlycontradictory concerns is to modify the watermark pattern such that wheninserted at high enough strength for detection it introduces minimalperceptual degradation.

In view of the prior art, there is a need for a method for inserting awatermark into digitized data for copy generation management which canbe done at the recorder stage and thus requires minimal computationaleffort and associated costs. There is also a need for a method whichinserts a watermark of a significantly lower strength then previouslyused in the prior art that can be detected with high likelihood.

SUMMARY OF THE INVENTION

Therefore it is an object of the present invention to provide a methodfor data preparation and watermark insertion which requires a minimalcomputational effort at the recorder stage.

It is a further object of the present invention to provide a method fordata preparation such that subsequent watermark insertion is inexpensiveas compared to the methods of the prior art.

It is yet a further object of the present invention to provide a methodfor data preparation and watermark insertion which results in awatermark of a significantly lower strength, then previously done in theprior art, which can be detected with high likelihood.

It is still yet a further object of the present invention to provide amethod for data preparation and watermark insertion for copy generationmanagement which addresses all of the above objectives.

The method of the present invention differs from the typical approach inthat not only is the watermark pattern carefully chosen to satisfy thetradeoff between high likelihood of detection and high perceptualsimilarity between watermarked and original data, but the method alsomodifies the characteristics and signals derived from thecharacteristics of the original data to reduce the interaction betweenthe data characteristics and the watermark characteristics. This allowsfor a watermark of a significantly lower strength to be detected withhigh likelihood.

To achieve these advantages over the prior art, a method for datapreparation and watermark insertion is provided. The method comprisesthe step of preparing the data at a first time by manipulating at leastone set of the data characteristics for subsequent insertion of a firstwatermark. In a preferred embodiment of the method of the presentinvention the method further comprises the step of inserting the firstwatermark by manipulating the set of data characteristics at a secondtime subsequent to the first time. In still yet another preferredembodiment of the method of the present invention, the method furthercomprises the step of inserting a second watermark at a third time,before, during, or after the first time, by manipulating at least oneset of the data characteristics.

In a variation of the present invention a method for inserting awatermark into compressed data is provided. The compressed data has setsof data characteristics. The method comprises the steps of inserting awatermark by manipulating the set of data characteristics; andoptimizing the manipulated data by modifying the compressed datacharacteristics subject to a set of constraints.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the methods of thepresent invention will become better understood with regard to thefollowing description, appended claims, and accompanying drawings where:

FIG. 1 illustrates a typical method of watermark insertion of the priorart.

FIG. 2 illustrates the method of watermark preparation and insertion ofthe present invention.

FIG. 3 illustrates a flow chart generally outlining the steps of thepresent invention in the context of compressed data which iterates overall intracoded blocks.

FIG. 4 illustrates a flow chart specifically outlining the steps of thepresent invention in the context of compressed data for each intracodedblock iterated over all contributing coefficients.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Although this invention is applicable to numerous and various types ofdigitized data, it has been found particularly useful in the environmentof digital video data and copy generation management. Therefore, withoutlimiting the applicability of the invention to digital video data andcopy generation management, the invention will be described in suchenvironment.

The technique presented here is intended for an application in which twocopy protection watermarks are inserted into image, audio, or videodata. Prior to distribution, when ample computing resources may beavailable, the data is preprocessed for insertion of a watermark whichwill be referred to as the first watermark. While the data ispreprocessed or prepared for insertion, the first watermark is notactually inserted at this time. Also prior to distribution, a secondwatermark may be added to the data. The second watermark is used toindicate to a consumer recording device such as digital versatile disk(DVD), digital video home system (VHS), digital audio tape (DAT) orrecordable compact disk (CD-R) that no or one copies are allowed to bemade. In the event that no copies are allowed, the recording device willprohibit such copies. In the event that one copy is allowed, therecording device will allow copying, but will insert the first watermarkinto the copy. In the event that the first watermark is already present,further copying is disallowed. The method of the present inventionencompasses the preparing of the data for the first watermark, alongwith the preferable steps of, inserting the first watermark, inserting asecond watermark, and inserting the first watermark specifically intocompressed data.

Before describing the method of the present invention in detail thefollowing overview of the three preferred steps of the present inventionare discussed. In a preferred embodiment of the method of the presentinvention, the method comprises a first step of preparing the data at afirst time by manipulating at least one set of the data characteristicsfor subsequent insertion of a first watermark, a second step ofinserting the first watermark by manipulating the set of datacharacteristics at a second time subsequent to the first time, and athird step of inserting a second watermark at a third time, before,during, or after the first time, by manipulating at least one set of thedata characteristics. These steps will now be discussed in detail below.However, it should be understood by someone skilled in the art that thefirst step alone is novel as compared to the prior art and that itscombination with the next two steps is given by way of example only andnot to limit the scope of the invention.

Preparation

A novel feature of the method of the present invention is thepreparation of the data to be watermarked. The preparation allows for awatermark of low strength to be subsequently inserted such that thewatermark can be detected with high likelihood.

Referring now to FIG. 2, there is illustrated the method of the presentinvention in which the original data is prepared for subsequentinsertion of the first watermark. Instead of the watermark pattern 2,referred to as the first watermark, being added directly to the originaldata 1 as is done in the prior art, the watermark pattern 2 is added toa modified version 7 of the original data 1. The modification processthat generates the modified version 7 from the original data 1 is calledthe preparation stage. The two important properties of the modified dataset 7 are that it is perceptually similar to the original data 1 and thedata characteristics or signal derived from the data characteristics 8is maximally different from that of the watermark data 5.

In preferred applications of this invention, the original data may beaudio, video, or still imagery. The set of data characteristicsconsidered may be derived from the data in the spatial domain, thetemporal domain, and/or a transformed domain. There are many transformeddomains from which data characteristics can be derived. In the preferredimplementation the data characteristics are derived from the data inboth the spatial and the block DCT domains. Other local transformdomains such as block Fourier transform, Hadamard transform, cortextransform, and wavelets as well as global transform domains such as theDCT and Fourier transform may be used. Spatial and temporal domaincharacteristic that can be used include sample value, edge features,color characteristics, textures, and phonemes.

The signals shown in FIG. 2, namely the signal derived from thecharacteristics of the original data 4, the signal derived from thecharacteristics of the watermark 5, the signal derived from thecharacteristics of the watermarked data 6, and the signal derived fromthe characteristics of the prepared original 8 are derived from the datacharacteristics. The data characteristics are mapped to some signalhaving measurable features that will serve as the basis of thecomparison in the detection process. The modified version of the data 7,after preparation, will have a derived signal 8 that matches somecriterion. In the preferred implementation, the criterion is minimumvariance of the derived signal. In other words, we seek to make thederived signal as flat as possible. In general the data is modified suchthat the derived signal matches a target signal. Without loss ofgenerality, this can be viewed as minimizing an error function, E,defined by equation 1:

 E=S−T  (1)

where S is the derived signal 8, and T is the target signal. In thepreferred implementation we can consider the target signal, T to be aconstant.

Insertion of First Watermark

Once the data has been prepared as described above, the first watermarkcan be added. Again, referring to FIG. 2, the preparation step hasmodified the unwatermarked data such that a signal 8 derived from a setof data characteristics has a known form. Using an error function asdescribed above to shape the data characteristics, the derived signal 8is preferably flat, as discussed previously, with average value close tozero. The watermark pattern 2 is designed such that the signal 5 derivedfrom the same set of characteristics, this time extracted from thewatermark pattern, is significantly different and easily distinguishablefrom the flat, zero mean signal 8 derived from the prepared data. Theamplitude or strength of the watermark pattern 2 relative to theprepared data 7 may be very small while the signal derived from thewatermarked data 6 will be sufficiently similar to the signal derivedfrom the watermark pattern 5 to indicate a positive detection decision.

Insertion of the first watermark involves a modification of theunwatermarked data such that a set of data characteristics, or a signalderived from a set of data characteristics, will closely match a knownwatermark signal, alternately referred to as a signal derived from a setof characteristics of a watermark pattern. The set of datacharacteristics considered may be derived from the data in the spatialdomain, the temporal domain, and/or a transformed domain. There are manytransformed domains from which data characteristics can be derived. Inthe preferred embodiment, the data characteristics are derived from thedata in both the spatial and the block DCT domains. Other localtransform domains such as block Fourier transform, Hadamard transform,cortex transform, and wavelets as well as global transform domains suchas the DCT and Fourier transform may be used. Spatial and temporaldomain characteristic that can be used include sample value, edgefeatures, color characteristics, textures, and phonemes. In the spatial,temporal, and transformed domains the two step insertion process canreduce to the addition of a fixed pattern to the data. This reduction incomplexity occurs because the data dependent, adaptive computationswhich are involved in typical watermark insertion (dependence on datacharacteristics discussed above) have been incorporated in thepreparation stage. In the preferred embodiment the data characteristicused is an average of many block DCT coefficients from various locationsin the data. The insertion step may also be performed in a compresseddomain. Examples of common video compression techniques in which thismethod is applicable are MPEG, MEPG2, H.261, and H.263. JPEG is a goodexample of a still image compression technique in which the watermarkpreparation and insertion method of the present invention is applicable.In general, these compression techniques involve block DCTtransformation of images or image frames (intracoding) or differenceimages (intercoding). In the later case the differences are typicallybetween two video frames adjacent in time where one or both may beoriginal frames or approximations to original frames. These compressiontechniques also contain a final, lossless entropy coding step. Ingeneral, the compressed data must be entropy decoded prior to watermarkinsertion. Some compression techniques allow for compressed frames inwhich both intra and inter coded blocks are present. The first watermarkdescribed is preferably inserted only into the intracoded blocks.

Referring now to FIG. 3, there is illustrated a method of insertion of afirst watermark into compressed data, the method generally referred toby reference numeral 300. The insertion into compressed data is aprocess in which each intracoded block is examined and modified. Thismodification is made to optimize the similarity of the watermark signaland the signal derived from the characteristics of the watermarked dataunder certain constraints, considering all changes made so far, andassuming no further changes will be made. Three important constraintsare used. A fidelity constraint limits the maximum perceptual differencebetween the watermarked data and the prepared data. A bitrate constraintinsures that the size of the compressed watermarked data does not differfrom the compressed unwatermarked data. A level constraint restricts newwatermarked values to be such that they will not be changed bysubsequent quantization. Such quantization is usually required prior toreintroduction of the entropy coding.

In summary, method 300 comprises the steps of analyzing each block ofthe processed data at step 302. When all blocks have been analyzed, themethod 300 proceeds along route 302 a to step 304 where it terminates.If there exists any blocks not yet analyzed, the method 300 proceedsalong route 302 b to step 306 where a signal is derived from a set ofdata characteristics. At step 308 the method 300 determines the set ofall possible changes that satisfy the constraints. At step 310 thechange that would optimize the similarity between the derived signal andthe target watermark in the absence of any future changes is selected.The method 300 then loops back to step 302 until all blocks have beenanalyzed.

It should be understood that the method as illustrated in FIG. 3 isgiven by way of example only, and not to limit the scope of theinvention.

insertion of Second Watermark

The second watermark can be inserted at any time relative to thepreparation or to insertion of the first watermark. The combination ofthe second watermark and the preparation for the first watermark allowfor powerful applications. Typically the set of data characteristicschosen for the second watermark should be disjoint from that chosen forthe first watermark to avoid interaction between the two watermarks orinteraction between the preparation process (for the first watermark)and the second watermark. However non-disjoint sets can also besupported.

EXAMPLES

Copy Generation Management:

In a preferred embodiment of the present invention in which thewatermarks are used in a copy generation management scheme, it ispreferable to add an additional watermark at the time of recordingrather than to remove a watermark. The additional watermark is the firstwatermark discussed previously, which is computationally easy to insertand thus low cost hardware and/or software is capable of doing so, suchas consumer DVD and VHS recorders. The first watermark also must notdegrade the image fidelity and, at the same time, must be robust tosubsequent signal transforms, e.g. survive digital-to-analog andanalog-to-digital conversion.

Insertion of the “copy once” watermark, referred to previously as thesecond watermark is computationally expensive since significant analysisof the image is performed to determine the perceptually importantregions of the image. Thus, such an insertion procedure is not practicalfor the first watermark, yet the first watermark should have many of thecharacteristics of the more robust “copy once”, second watermark. Inthis example, much of the computation associated with the firstwatermark is performed offline during the preparation stage, typicallyduring production, such that a lightweight computational procedure canthen be employed at the recorder i.e., the player stage, in order toinsert the first watermark.

Specifically, the second watermark is inserted into a set of averagedfrequencies in the image. During or after insertion of the secondwatermark, a disjoint set of average frequencies are flattened orprepared for the subsequent insertion of the first watermark.

This preparation uses the same procedure as the second watermark, i.e.sophisticated perceptual models may be employed to best determine howthe averaged frequencies can be flattened. This procedure prepares theimage for the subsequent insertion of the first watermark.

Insertion of the first watermark adds a unique watermark that representsthe “copy-no-more” state. The strength of the first watermark issignificantly less than that commonly used for the second watermark.This is because the first watermark does not need to override the“noise” present in the image. This noise, a function of the naturallyoccurring signal that is the image, has been eliminated during thepre-processing phase where it is set to zero.

The first watermark has the same basic structure as other watermarks,e.g., it is preferably a N-bit binary vector In the preferred embodimentN=64 however other values of N may be preferred to obtain higher datarates or lower computational costs.

Insertion of the First Watermark into a MPEG-2 Bitstream:

In a preferred example of the method of the present invention, analgorithm for inserting the first watermark directly into the DCTcoefficients of an MPEG-2 stream is provided. The first watermark isinserted into intracoded blocks of an MPEG-2 layer. This may be the baselayer of the MPEG-2 stream or an enhancement layer. This method can beapplied to an MPEG-1 data stream as it qualifies as a valid MPEG-2 baselayer. This watermark insertion method affects neither the overallbitrate nor the starting positions of the slices in the MPEG-2 stream.The detection process is the same as that for the first watermark thathad been inserted directly into the baseband video and the same as thatfor the second watermark. Detection processes for detecting the presenceof a watermark in digital data are well known in the art.

The goals of this technique are to insert the first watermark (increasethe likelihood that it will be detected), maintain the overall bitrateand position of I-frames within the data stream, and control thestrength of the first watermark for both detection and visibility.

The method can be explained as follows. The 8×8 intracoded blocks of anMPEG stream are stored in the discrete cosine transform (DCT) domain.The location of the block within the image and the location of eachcoefficient within the 8×8 block together specify to which, if any,watermark element that coefficient contributes. It is possible topredict the effect of an increase in a coefficient value on thecorrelation between the extracted and target watermarks. This effect mayagain be dependent on both the coefficient location within the 8×8 blockand the block position within the image. It may also be dependent on thetype of coding associated with the macroblock of which the current blockis a member (field or frame based DCT). Alternatively, it is possible topredict which change, positive, negative, or none, will increase thecorrelation between the extracted and target watermarks. Based on thisprediction, the image can be examined on a block-by-block basis and makecoefficient changes which will increase the expected correlation. It isto be assumed that an increase in correlation will, in general, increasethe correlation coefficient and thus the detection certainty.

This method maintains the bitrate by insuring that the position in thedata stream of the start of each slice or group of macroblocks does notchange. This is done by requiring that any changes made, use the same orfewer bits to encode. If fewer bits are used and the slice becomesshorter, bits are padded onto the end of the slice to restore thestarting position of the next slice in the data stream. These extra bitscan instead be used in the slice to allow coefficient changes that usemore bits to encode. We track these extra bits or saved bits, increasingthe count when a change decreases the required encoding bits anddecreasing the count when a change increases the required encoding bits.The count of saved bits is not allowed to drop below zero. Thus, achange which increases the number of bits required for encoding isallowed only if there are enough bits saved from previous changes. Atthe end of the slice, the count of saved bits is reset to zero and thosebits are padded into the data stream.

More specifically, MPEG stores the 63 AC coefficients of an intracodedblock as run/value pairs, one pair for each non-zero coefficient. Thevalue element of the pair refers to the signed magnitude of a non-zerocoefficient. The run element refers to the number of zero valuedcoefficients directly preceding that non-zero coefficient. Eachrun/value pair is encoded with a unique binary code, called a variablelength code (VLC). In order to maintain the bitrate, only non-zerocoefficients are considered and possible changes are evaluated based onthe lengths of the original VLC and of that which would be necessary toencode the modified run/value pair.

In addition to controlling the bitrate in the data stream, we wish tocontrol the first watermark strength for detection and visibility. Astronger first watermark will be more detectable (increased likelihoodof detection) but is also more likely to be visible. Within each block,the watermark strength is controlled for detection by a single value.This is the maximum amount of change allowed in the block. Once thismaximum amount of change has been effected, no further changes areallowed.

The change within a block is distributed among the non-zero coefficientsaccording to a frequency-based perceptual model. This is to control thevisibility of the inserted first watermark. A frequency-based perceptualmodel is used to determine the relative insensitivity of the humanvisual system (HVS) to the 63 AC DCT coefficients in an 8×8 block. Theserelative insensitivities are referred to as slacks. These slacks aredependent on the type of coding associated with the macroblock of whichthe current block is a member (field or frame based DCT).

Referring now to FIG. 4 there is illustrated a flow chart of theinsertion method, referred to generally by reference numeral 400.MaxBlockChange refers to the strength for detection control aspreviously described. NumContrib is the number of non-zero ACcoefficients for which a positive or negative change will increase thedetected correlation. These coefficients are said to contribute to thecorrelation. TotalSlack is initialized as the sum of the slacks of allcoefficients which contribute to the correlation at step 402. The method400 loops over all contributing coefficients at steps 404 through 412starting at the highest in the MPEG zig-zag scan order. The maximumchange allowed for any coefficient is calculated at step 404 as theRemainingChange for the block weighted by the slack of that coefficientrelative to the total remaining slack. The actual change is then foundwithin the constraint of MaxChange and the constant bitrate constraintpreviously described. The function ConstBitRate effects this change andupdates the SavedBits count at step 406. The TotalSlack is then updatedat step 408 to represent the sum of the remaining slacks and theRemainingChange is updated, also at step 408, to represent the maximumamount the remaining contributing coefficients in the block may change.After all the contributing coefficients in the MPEG zig-zag scan orderare processed the method 400 terminates at step 414.

While there has been shown and described what is considered to bepreferred embodiments of the invention, it will, of course, beunderstood that various modifications and changes in form or detailcould readily be made without departing from the spirit of theinvention. It is therefore intended that the invention be not limited tothe exact forms described and illustrated, but should be constructed tocover all modifications that may fall within the scope of the appendedclaims.

What is claimed is:
 1. A method for data preparation and watermarkinsertion, the data having sets of data characteristics, the methodcomprising the steps of: providing data to be watermarked; selecting atarget signal; extracting a derived signal from a set of datacharacteristics; preparing the data at a first time to improvedetectability of a subsequently inserted first watermark signal and/orreduce the complexity of the subsequent insertion of the first watermarksignal by manipulating at least one set of the data characteristics suchthat the derived signal substantially matches the target signal; andinserting the first watermark by manipulating the set of datacharacteristics at a second time subsequent to the first time.
 2. Themethod of claim 1, further comprising the step of inserting a secondwatermark at a third time, before, during, or after the first time, bymanipulating at least one set of the data characteristics.
 3. The methodof claim 2, wherein the set of data characteristics manipulated for thesecond watermark are disjoint from the manipulated set of datacharacteristics for the first watermark.
 4. The method of claim 3,wherein the set of data characteristics manipulated for the secondwatermark and the set of data characteristics manipulated for the firstwatermark are disjoint in a spatial domain and/or a temporal domainand/or a transformed domain.
 5. The method of claim 1, wherein the datais a representation of an image.
 6. The method of claim 1, wherein thedata is a representation of audio.
 7. The method of claim 1, wherein thedata is a representation of video.
 8. The method of claim 1, wherein theset of data characteristics are spatial domain characteristics.
 9. Themethod of claim 8, wherein the spatial domain characteristics are chosenfrom a group consisting of pixel intensities, edge features colorcharacteristics, and textures.
 10. The method of claim 1, wherein theset of data characteristics are transformed domain characteristics. 11.The method of claim 10, wherein the transformed domain characteristicsare chosen from a group consisting of DCT, block DCT, FFT, block FFT,wavelet, Hadamard transform, Cortex transform.
 12. The method of claim1, wherein the manipulating of the data characteristics is such that asignal is derived therefrom which substantially matches a pre-selectedsignal.
 13. The method of claim 12, wherein the pre-selected signal haszero variance.
 14. The method of claim 12, wherein the derived signal isperformed by averaging subsets of the sets of data characteristics. 15.The method of claim 1, wherein the manipulating of the datacharacteristics is such that an error function is minimized.
 16. Themethod of claim 15, wherein the error function is a measure of variance.17. The method of claim 1, wherein the inserting step occurs in aspatial and/or time domain.
 18. The method of claim 17, wherein thespatial and/or time domain characteristics are chosen from a groupconsisting of pixel intensities, edge features, color characteristics,textures.
 19. The method of claim 1, wherein the inserting step occursin a transformed domain.
 20. The method of claim 19, wherein thetransformed domain characteristics are chosen from a group consisting ofDCT, block DCT, FFT, block FFT, wavelet, Hadamard transform, Cortextransform.
 21. The method of claim 1, wherein the inserting step occursin a compressed domain resulting in compressed data.
 22. The method ofclaim 21, wherein the compressed domain is chosen from a groupconsisting of MPEG1, MPEG2, JPEG, Quicktime, H.261, H.263.
 23. Themethod of claim 21, wherein the compressed data is video and the firstwatermark is inserted into only intracoded portions of the compressedvideo data.
 24. The method of claim 21, wherein the further manipulationincludes an optimization procedure that modifies the compressed datacharacteristics subject to a set of constraints.
 25. The method of claim24, wherein the optimization procedure comprises the substeps of: (i)obtaining a set of values from the compressed data; (ii) determining aset of changes to the data that satisfy the set of constraints; (iii)choosing a change from the set of changes that optimize detection of thewatermark in the absence of any future changes; and (iv) repeating steps(i) through (iii) until all the compressed data is processed.
 26. Themethod of claim 25, wherein the set of constraints comprises fidelityconstraints.
 27. The method of claim 25, wherein the set of constraintscomprises bitrate constraints.
 28. The method of claim 25, wherein theset of constraints comprises constraining each value in the compresseddata to a known quantization level.
 29. The method of claim 24, whereinthe set of constraints comprises fidelity constraints.
 30. The method ofclaim 24, wherein the set of constraints comprises bitrate constraints.31. The method of claim 24, wherein the set of constraints comprisesconstraining each value in the compressed data to a known quantizationlevel.
 32. The method of claim 1, wherein the first time occurs prior todata distribution and wherein the first watermark is inserted into thedata at the time the data is copied.
 33. The method of claim 32, furthercomprising the step of prohibiting the copying of the data if the firstwatermark is present.
 34. The method of claim 33, wherein theprohibiting step is implemented in a consumer recording device.
 35. Themethod of claim 34, wherein the format of the recording device is chosenfrom a group consisting of DVD, DHVS, DAT, and CD-R.
 36. The method ofclaim 1, wherein the set of data characteristics are time domaincharacteristics.
 37. The method of claim 1, wherein the set of datacharacteristics are spatial and time domain characteristics.